I am a biological anthropologist investigating evolutionary and ecological influences on growth and development, and the implications of those relationships for public health. My research, conducted with two indigenous populations—the Tsimane of Bolivia and the Qom/Toba of Argentina—combines field research (focal follows, ethnographic observations, interviews) with laboratory analysis of non-invasive biomarkers and mixed-modeling approaches. My specific investigative questions have been informed by two related tenets of evolutionary biology relevant to human health: (1) that nutritional and ecological conditions in early life can influence metabolic, immunological, and reproductive responses to stimuli in later life, and (2) that many non-communicable diseases result from a mismatch between a people’s current environments, developmental calibrations to environments in early life, and our evolved biology and life history. In working with the Tsimane and the Qom, I am able to study health outcomes in relation to certain behavioral and ecological factors that are more representative of conditions during much of human ancestry—e.g. universal and prolonged breastfeeding, ubiquitous microbial exposure, high infectious disease burdens, early reproduction, and high fertility. At the same time, these study populations are experiencing rapid environmental and social changes affecting developmental and health outcomes across the life course, with broader implications for global health.